The invention relates to a system for desalinating water by inverse osmosis in pressurized chambers which provides some important features in regard to energy consumption, functionality and small size of the chambers by increasing the speed of the water for the filling and emptying thereof.
The Spanish patent application ES 9701877, owned by the same applicant, describes an inverse osmosis desalinating plant with pressurized mother chambers in the form of cylinders inside of which a piston circulates for separating different salinity water masses. Even though the plant""s operation is extremely satisfactory, it is observed that, in the case of large-size facilities, it is not advisable to invert the movement of the water masses and the piston at the end of each of the mother chamber pressurizing cycles in view of the considerable kinetic energy that needs to be dissipated.
The present invention is based on a substantially different concept, namely the continuous kinetic cycle, whereby the different salinity water masses circulating through the mother chamber always circulate in the same direction, without stopping, so that dissipating the kinetic energy of the moving water mass and subsequently accelerating it in the opposite direction becomes unnecessary. This results in considerable saving of energy, reduction in chamber size, improved reliability and longer equipment life.
The system is first and foremost characteristic in that the two or more pressurized mother chambers used for storing the water to be desalinated are no longer shaped in the form of a straight-line tube, and may be either fitted or not with a piston for separating the water to be desalinated and the brine. The chamber described hereunder is ring-shaped, so that the start and the end of the tube are connected and thus form a closed circuit, the tube being toroidal, continuous zigzag, helicoidal or otherwise shaped, no matter how whimsical or functional, the sole condition being that its start and end are connected to form a loop or closed ring circuit.
The second characteristic is that, when the system is fitted with a piston, said piston is sphere-shaped, like a ball, enabling it to circulate along the curves of the continuous tube, and that its weight is approximately that of the density of the water, so that it may be entrained in the flow and will not be centrifuged in the curves as a result of its excessive density. Any material may be used, such as metal, plastic, etc. An xe2x80x9celasticityxe2x80x9d feature may also be added, such as that present in rubber, which offers very little friction when wet and is capable of adequately withstanding direction changes or slight impacts against the walls, and it may even be formed by an accumulation of low-hardness gels, rubbers or elastomers such as the silicones used in mammary prostheses, or even a simple hollow rubber ball filled with water or some other substance providing it with sufficient resiliency to adapt to the route.
The third characteristics refers to recovery or parking mechanism for the ball or piston, a kind of basket or baseball glove, installed for receiving the sphere and sending it back along the same route, combined with a fluid bypass through a non-return valve of a special design which is opened by water""s inertia, in a manner that, upon closing the entry of the water into the chamber, the mass rotating inside the chamber is not restricted but is free to circulate inside the ring at the expense of the kinetic energy contained in the moving mass, which need not be stopped and then placed in motion again as in the case of an alternate movement piston, the only element needing to be stopped being the small mass of the sphere-shaped piston, if fitted.
The system also comprises valves, pumps and a piston-position detecting system, all of which operate in programmed fashion to achieve the desired result.
In order to solve the above problems, several improvements have finally been introduced in inverse osmosis water desalination plants with continuous kinetic cycle mother chambers which, without substantially modifying the operation principles set forth, greatly simplify their practical embodiment.
The first improvement consists in introducing two three-way slide valves mechanically coupled onto one another. The normal and simple condition in a three-way slide type valve fitted with cylinder and radial ports is for the slide to be fitted with a single groove and for the central intake of the three port lines to be the common inlet or outlet, so that when the slide is at one end, the ports on that side are connected to the center, and when at the other end, that other side is connected also to the center. The previously described six-way double-groove valve presents a problem in that the times needed for filling and emptying the mother chambers are not the same, and thus the volumes that have to be handled in one chamber and the other are different. This is because the closing and opening time sequences are not the same in each chamber, since the first chamber to close is the last to open, and during this time frame the second chamber has to open and close, the operational time of this second chamber thus being much shorter. There are two means of solving this problem: the fist solution consists in providing one of these three-way valves with a double groove in order to invert the operation, namely the ports which in the first case are open, are now closed, and vice-versa; the second solution consists in dividing the valve into six ways, i.e. a double set of three ways, and invert the operational direction of one in respect to the other. This second solution requires the inclusion of a mechanism providing movement to one slide in one direction while the other slide is moving in the opposite direction.
This justifies the selection of two three-way valves, one of them being fitted with the double groove slide, although more can be said on the subject. The valves proposed are slide-type valves with radially arranged ports in the form of circular holes which provide for pressure compensation. Furthermore, the valves are fitted with a double sleeve or external housing which delimits several collecting chambers for these ports, individualized by means of ring separators. These chambers play an important role here, not only related to the manifold communicating the external connections with the corresponding ports, but in that they allow the water to pass from the mother chambers when the circulation valves open, the water from the mother chambers being able to circulate in a continuous kinetic cycle; this means that, when liquid is trapped because the valves are closed to the exterior, the recirculation valves open as a result of the kinetic energy, with the water circulating over itself in a closed loop, thus avoiding ramming impacts and maintaining the water mass in motion until the next and immediate operation comes along.
The second improvement consists in depressurizing the mother chambers prior to unloading the brine to the exterior; this increases the service life of the recirculation valves, which are thus able to operate in a less demanding manner. This prior depressurizing is performed through ports of a very small section which open immediately before the main discharge ports.
As is well known, there are several means of operating the various types of slide valves, either hydraulic or mechanical, and their positioning is no problem given the present numeric control computer systems, stepper motors and similar devices available. Thus, the third improvement consists in a very simple mechanical driving mechanism operated by a constant angular motion shaft such as an electric motor shaft through a speed reduction box, which makes the valve""s slides to stop at each end when the mother chambers are being filled or emptied, and which furthermore is provided with a slight stop or reduced speed at a point in its stroke corresponding to the xe2x80x98prior pressurizingxe2x80x99 operation, as described in Spanish patent application ES 9800098, enabling the mother chambers to capture the high pressure from the membranes, the rest of the stroke being performed as fast as possible. This is achieved through a mechanism of planetary gears having appropriate diameters, with any point of the planetary gears moving through an epicycloid trajectory.
Inside the valves, the water suffers abrupt direction changes which make the flow to be fairly turbulent, all the more so if the water flows at a relatively high speed designed to reduce the size of the valves. However, removal of the prior art movable pistons requires the flow be as laminar as possible in order to avoid the separation surface between the water masses with a different salinity level from becoming excessively deformed, leading to the mixing of the masses. The object of the fourth improvement is to reduce the turbulence, and this is achieved by installing flow laminators at the valve outlets.
The following advantages are evident in the desalinating plants produced according to the above mentioned four improvements in respect to the prior art:
1. Both in the Spanish patent applications ES 9600294 and ES 9800098 and in the initial concept of the continuous kinetic cycle mother chambers, too many xe2x80x98Txe2x80x99 connections are used between the pipes, the valves and the mother chambers. This impairs the hydrodynamics in the system. In this case, this problem is greatly reduced.
2. The use of separate valves for each operation is more costly and more difficult to synchronize than the use of one single six-way valve. This solution can be further improved if the system is fitted with two double sleeve three-way valves, i.e. with the two cylindrical bodies placed concentrically, operated simultaneously. This improves the fluid""s hydrodynamics, in addition to facilitating access to the various parts for assembly, maintenance or repair purposes, in view that all the valves are grouped in a very compact design, thus enabling their size to be reduced and providing an esthetic and functional final design. It should be borne in mind that 14 valves are necessary: 4 mechanically driven valves (which, when simplified, comprise two three-way units), 4 single direction non-return valves, 2 recirculation valves for each chamber (these two valves constituting the key element in the system for preventing the slowing down of the fluid and for implementing the continuous kinetic cycle), 2 prior pressurizing valves, and 2 prior depressurizing valves.
3. Production raw material and labor costs are substantially reduced, access for replacement, repair or maintenance is improved, and, above all, the complete set of desalinating plant operation valves can be easily transported, with only pipework assembly and pump connection tasks being performed on-site.
4. A perfect solution is given to the operation assymetry problem caused by the six-way valve, in that this valve, as described, requires both mother chambers to be provided with different operation times and therefore different volumes.